A light emitting diode (LED) is a semiconductor element converting electrical energy into light such as ultraviolet light, visible light or the like, and has advantages that it has a long life and high reliability, and when the LED is used as a light source, the time which exchanges lamps can be saved. A light-emitting device (LED lamp) having an LED element sealed with, for example, a transparent resin is used extensively as a component part for various types of displays such as portable communication devices, PC peripheral devices, office automation equipment, home electric appliances, signal equipment, various types of switches, backlight type display panels, and the like.
For example, the light-emitting device using the LED element has a structure that the LED element is fixed onto a substrate and each of electrodes of the LED element is electrically connected to terminal on the substrate via a conductive wire, respectively. In addition, a reflector for reflecting light irradiated from the LED element is disposed around the LED element. For example, a light-emitting layer having phosphor particles is filled in the reflector (see, for example, Reference 1).
The color tone of light emitted from the light-emitting device is not limited to the light emission wavelength of the LED element, and visible light ranging from blue to red can be obtained depending on usages by, for example, a phosphor dispersed into the light-emitting layer. Especially, a white light-emitting type light-emitting device is useful as a backlight for the liquid crystal display of portable communication devices and PCs (see, for example, Reference 2).
The conventional light-emitting device having the LED element and the reflector disposed on the substrate has a drawback that emission luminance tends to become low. In other words, since the conductive wires extended from the electrodes of the LED element are connected to the terminals on the substrate, the reflector cannot be approached enough to the periphery of the LED element. Therefore, there is a space enough for disposition of the conductive wires between the reflector and the LED element. Light irradiated from the LED element is diffused needlessly within the light-emitting layer before it reaches the reflector and not irradiated enough to the reflector, so that the emission luminance becomes low.
To avoid the lowering of the emission luminance, there is, for example, a method that the conductive wires extended from the LED element are connected to the terminals on the substrate, which are located outside of the reflector, and the space between the LED element and the reflector is decreased. But, since this method forms a connection point of the conductive wire outside of the reflector, the same portion cannot be used effectively for other usages. In addition, since the conductive wires must be disposed over the top of the reflector, the conductive wires become long, and the productivity and reliability of the light-emitting device are lowered.
Meanwhile, as a method that unnecessary diffusion of light within the light-emitting layer is suppressed while the distance between the LED element and the reflector is remained as it is, the amount of a phosphor contained in the light-emitting layer may be decreased. But, such a method causes further lowering of the emission luminance because the content of the phosphor is decreased.
[Reference 1]JP-A 2002-198573 (KOKAI)[Reference 2]JP-A 2003-160785 (KOKAI)